METHOD FOR STARTING A SINGLE-PHASE INDUCTION MOTOR, STARTING DEVICE FOR A SINGLE-PHASE MOTOR AND STARTING SYSTEM THEREFOR

Description

[0001] The present invention relates to a method of starting a single phase induction motor specially designed to optimize the starting time of said motor depending on its size and operating load.

[0002] The present invention further relates to an electronic starting device of the type used in electric motors, particularly in single-phase induction motors.

[0003] Additionally, the present invention relates to a system for starting single phase induction motors which includes the device and method proposed herein.

Description of the Prior Art

[0004] Single-phase induction motors are widely used due to their simplicity, robustness and high performance. Their application is found in household appliances in general, refrigerators, freezers, air conditioners, hermetic compressors, washing machines, motor pumps, fans and some industrial applications.

[0005] Known induction motors generally consist of a cage rotor and a wound stator comprised of two windings, one of them a running winding and the other a starting winding. During normal operation of the compressor, the running winding is fed by alternating current, and the starting winding is fed temporarily, at the beginning of the starting operation, creating a rotating magnetic field in the stator air gap, a condition necessary to accelerate the rotor and bring about its start.

[0006] The rotating magnetic field can be obtained by supplying the starting winding with a current lagging in time relative to the circulating current through the primary winding, preferably at an angle close to 90 degrees. This discrepancy between the current flowing in both windings is achieved by constructive characteristics of the windings or by installing external impedance in series with one of the windings, although typically in series with the starting winding. The value of the circulating current through the starting winding during the starting process of the motor is normally high, making it necessary to use some type of switch that would interrupt this current after the time required to bring about the motor's acceleration has passed.

[0007] For motors in which very high efficiency is required, the starting winding is not fully switched off after the expiration of the starting period, as a capacitor called the operating capacitor remains in series with this winding, providing sufficient current to increase the maximum torque of the motor and its efficiency.

[0008] For motors with this configuration using a permanent impedance in series with the starting winding during normal motor operation, several PTC-type starting devices are known, electromechanical relay, timed, as well as combinations in which a PTC connected in series with a device which interrupts the flow of current after a determined period of time (RSP) as cited in U.S. patent documents 5,053,908 and U.S. 5,051,681, and in the copending international patent application WO 02/09624 A1, from the same applicant.

[0009] One of the components widely used in starting "split-phase" single-phase motors, where an operating capacitor is not used, is the electromechanical relay type. Its extensive use is related to its low manufacturing cost and its technological simplicity. On the other hand, the electromechanical relay presents a number of limitations chief among which are the need for the design of a specific component for each size of electric motor, the impossibility of its use in high efficiency engines where an operating capacitor is used, the generation of electromagnetic noise and sounds during its operation and the wearing of components caused by electric arcing and mechanical friction.

[0010] An alternative to the electromechanical relay is the PTC-type ("Positive Temperature Coefficient") device. This component is widely used in high efficiency engines where its application is associated with an operating capacitor. As it involves the use of a ceramic chip with no moving parts, its principle resolves many of the limitations of the electromechanical relay. As its operation is based on the heating of a ceramic chip, resulting in its increased resistance and the consequent limitation of circulating current, dissipation of residual power occurs over the entire period of its operation.

[0011] Another limitation of this component is related to the time interval required between consecutive starts. One of its major advantages is the possibility of using a single component to operate the start of a set of motors of a specified voltage (115V or 220V), but becomes a limitation when the feature under consideration is optimization of the energization time of the secondary winding. Its conduction time is directly proportional to the volume of the ceramic chip and inversely proportional to the circulating current, resulting in a reduced starting time when applied to larger motors and too long a period of time when applied to smaller motors. These two facts result in a deficient starting of larger motors and higher energy consumption during the starting period in smaller motors.

[0012] While timed starting components eliminate the major drawback of residual consumption of the PTC, they, however, do not allow one to adapt the starting time required for motors of different sizes. Its concept does not allow for the sizing of a circuit which provides the optimal starting time for different motor sizes, and it becomes necessary to have several models, each of them set to a given operating time and to suit a particular family of electric motors, resulting in de-standardization, increased changes in manufacturing lines and higher inventory. Such devices do not take into account the operating conditions at the moment of start-up and are therefore sized for the worst condition, thus increasing starting time. Starting circuits for single-phase induction motors are known from documents US 6756756 and US 7202627.

[0013] In view of the above, the present invention offers a new method of starting single-phase motors capable of optimizing the starting time of a wide range of motors, especially in terms of their operating power. Furthermore, a device and a starting system are also provided in order to achieve the objects of the present invention.

Objects of the Invention

[0014] It is a first object of the present invention to provide a cost-effective starting device with a simple and robust topology, which allows for:

i) large-scale use in low-cost systems, offering the advantages of timed devices in which residual power consumption is eliminated;

ii) the reduction of the number of components necessary for treating with a specific family of motors of the same supply voltage;

iii) the use of high-efficiency motors with operating capacitors, and that presents the feature of electromechanical relays, in which starting time is optimized in each different size of electric motor.

[0015] It is a second object of the present invention to provide a starting method for single-stroke induction motors that optimizes starting time in function of the size and motor load associated with the same.

[0016] It is another object of the present invention to provide a starting method for single-stroke induction motors that automatically optimizes starting time relative to the supply network voltage.

[0017] An additional object of the present invention is to provide an electronic device for starting a single-phase induction motor with negligible power consumption.

[0018] Furthermore, it is an objective of this invention to provide an electronic device for starting a single-phase induction motor that can operate in conjunction with a starting capacitor or any other impedance installed in series with the starting winding of the motor.

[0019] The present invention further aims to provide an electronic device for starting a single-phase induction motor that is not susceptible to transients or disturbances emanating from the supply network.

[0020] Finally, it is an objective of the present invention to provide an electronic device for starting single-phase induction motors that can operate in conjunction with the arrangement of some refrigeration systems having an impedance (resistance) connected in parallel with thermostat contacts used to generate a small amount of heat to keep the thermostat contacts free of moisture, but that also induce the appearance of residual voltages on the compressor terminals which disrupt or prevent the operation of some types of electronic devices that may erroneously construe such residual voltages as a functioning state of the compressor.

Brief Description of the Invention

[0021] The objects of the present invention are achieved by the provision of a method for starting a single-phase induction motor, the motor comprising a rotor and a stator having a running winding and a starting winding, the running winding and the starting winding being connected in parallel to an alternate voltage power supply, the starting winding being linked electrically to the starting device, the starting device comprising a start switch allowing connecting and disconnecting the starting winding to/from the voltage power supply under the control of an electronic signal-processing device, the starting device comprising a source of direct current supplied from the terminals of the start switch the electronic-signal processing device (30) being supplied by the source of direct current (29), the starting method comprising the following steps:

a-) first measuring via the starting device, the voltage between the terminals of the start switch and computing and storing an internal timebase by the electronic signal processing devicembased on a plurality of detected time instants when this voltage crosses zero before closing the start switch, the internal timebase being synchronized with the phase of the voltage power source,

b-) closing the starting switch S1 I, for initiating the supply of current to the starting winding B2 of the motor;

c-) measuring one or more starting time instants of the current in the starting winding B2 when this crosses zero;

d-) comparing the time instants Tpar where the current flowing through the starting winding B2 crosses zero with an internal timebase Tref;

e-) calculating via the starting device, a phase difference Df between the current flowing through the starting winding B2 and the internal base time Tref starting from the comparison made in Step e;

f-) opening the starting switch S1 based on the calculation of Step e, starting when the device detects the phase difference Df between the current flowing through the starting winding B2 and the internal timebase Tref, of a value greater than a pre-determined starting phase boundary Lfap.

[0022] The objectives of the present invention are also achieved by providing a system for starting a single-phase induction motor, the motor comprising a rotor and a stator having a running winding and a starting winding, the running winding and the starting winding being connected in parallel to an alternate voltage power supply F, the system comprising:

• a start switch linked electrically via its contact terminals to a source of alternate voltage, the start switch allowing connecting and disconnecting the starting winding to/from the alternate voltage power supply under the control of an electronic signal-processing device; - a DC power source supplied from the contact terminals of the start switch;
• the electronic signal-processing device fed by the direct current source and operatively linked to the start switch;
• a current zero-crossing sensor configured to detect time periods or time instants in which the current of the starting winding current crosses zero; and
• a voltage zero-crossing sensor at the terminals of the start switch configured to detect periods of time, or time instants, in which the voltage between the terminals of the start switch crosses zero;
• the system being configured that the voltage between the terminals of the start switch (S1) is measured and an internal timebase (Tref) is computed and stored by the electronic signal processing device (30) based on a plurality of detected time instants when this voltage crosses zero before closing the start switch (S1), the internal timebase (Tref) being synchronized with the phase of the alternate voltage power supply (F);
• the system being configured to close the start switch (S1) in order to initiate supply of current to the starting winding (B2) of the motor;
• the system being configured to open the start switch (S1) at the detection of a phase difference(Df) between the current flowing in the starting winding (B2) and the internal timebase (Tref) of a value in excess of a predetermined start phase boundary.

Brief Description of the Drawings

[0023] The present invention will be hereinafter described with reference to a preferred embodiment illustrated in the accompanying drawings of which:

Figure 1- shows a schematic diagram of a preferred embodiment of the electronic starting device and system, the object of the present invention;

Figure 2 - shows a graph illustrating the voltage waveform of the electronic starting device, in accordance with the teachings of the present invention; and

Figure 3 - shows a graph illustrating the timebase setting performed by the control unit of the starting device.

Detailed Description of the Drawings

[0024] Figure 1 illustrates a preferred embodiment of the object of the invention herein.

[0025] More particularly, the present invention provides a starting device 28 for a single-phase induction motor configured to provide means for ignition and shutdown of said motor in a very efficient and simplified manner.

[0026] This device 28 is essentially comprised of a start switch S1 and at least one direct current source 29 electrically linked in parallel to each other, as can be seen in Figure 1. Preferably, it is proposed to fit a single direct current source 29, however, one or more sources can be installed so as to supply the components and / or functional modules of device 28, which will be discussed in more detail below.

[0027] Said device 28 further comprises at least one electronic signal-processing device 30 powered electrically by the direct current source 29, and this device 30 is operably linked to the start switch S1 via a control terminal 26. Most preferably, the starting device 28 includes only one electronic signal-processing device 30 such as a micro-processor or micro-controller, however, two or more may be used without affecting the functioning and operation of this starter 28.

[0028] Some conventional components that are now well-known, such as micro-controllers from the Microchip family, ICPs or old micro-controllers from the INTEL family such as the 8051 and 8052, among others, can be easily used to build the electronic signal-processing device 30 in the present invention. Otherwise, this device 30 can also be made by a dedicated electronic circuit and designed from electronic components in general use.

[0029] Additionally, Figure 1 shows that the starting device 28 further comprises at least one voltage zero-crossing sensor SV electrically linked to the electronic signal-processing device 30 and to the start switch S1, and at least one voltage zero-crossing sensor RS electrically linked to the electronic signal-processing device 30 and to the start switch S1.

[0030] The starting device 28, in accordance with the teachings of the present invention, is configured to promote the starting and/or shutdown of the single-phase induction motor via the start switch S1.

[0031] In more detail, as can be seen in Figure 1, the starting device 28 connects through its start switch S1, the starting winding B2 to an alternate voltage source F. After motor start-up, the start switch S1 is brought into an open position by device 28.

[0032] An innovative feature of the present invention relates to the methodology, or method, of driving and control of motor start-up. Such a motor comprises a rotor and a stator M having a running winding B1 and a starting winding B2, as illustrated in Figure 1. From Figure 1 it can also be noted that the starting winding B2 is electrically linked to the aforementioned starting device 28, so that the running winding B1 is electrically linked to a source of alternate voltage supply F, or simply an alternate voltage source F.

[0033] More broadly, the present method is described below based on its main steps, namely:

a-) firstly measuring via starting device 28 the voltage between the terminals of the start switch (S1) and computing and storing an internal timebase (Tref) by the electronic signal processing device (30) based on a plurality of detected time instants (Tpar) when this voltage crosses zero before closing the start switch (S1), the internal timebase (Tref) being synchronized with the phase of the voltage power source (F),

b-) closing the start switch S1, for initiating the supply of current to the starting winding B2 of the motor;

c-) measuring one or more starting time instants Tpar of the current in the starting winding B2 where the latter crosses zero;

d-) comparing the times instants where the current flowing through the starting winding B2 crosses zero with the internal timebase Tref;

e-) calculating, via the starting device 28, the phase difference Df between the current flowing through the starting winding B2 and the internal timebase Tref based on the comparison made in Step e;

f-) opening the start switch S1 based on the calculation in Step g when the starting device 28 detects the phase difference Df between the current flowing through the starting winding B2 and the internal timebase Tref of a value in excess of a predetermined start phase boundary Lfap.

[0034] Figure 2 shows the voltage waveform present in the starting device 28, allowing for the identification of the critical moments of the start-up of the single-phase induction motor, according to the teachings of the present invention.

[0035] It is worth to note that in this case, the predetermined phase boundary Lfap depicts an operating state in which the motor is accelerated with a rotational speed close to its nominal operating speed. It is a fact that Step "d" above corresponds to the point at which the motor is initiating its start-up.

[0036] On the other hand, the phase boundary Lfap, as described, corresponds to the point at which the motor reaches substantially higher rotational speeds as compared to the beginning of the machine's start-up. When the electric motor is at a low speed or stopped, for example, the phase difference Df between the current flowing in the starting winding B2 and the calculated internal timebase calculated is considerably small in the present invention.

[0037] Operationally, to recap, we see that opening the start switch S1 is effected through a command sent by the electronic signal- processing device 30, which is incorporated in the starting device 28, as shown in Figure 1, at the moment when the motor is accelerated with a rotational speed close to its nominal value.

[0038] Alternatively, the present method further comprises a step of opening the start switch S1 when the phase difference Df between the current flowing through the starting winding B2 and the internal timebase Tref is larger than a predetermined phase value Fpred, which is configured to represent a state in which the motor is accelerated to a speed close to its nominal speed, after the expiry of a preset starting time starting Tppre.

[0039] Expressed in another way, the operational methodology of the object claimed herein also provides a step of opening the start switch S1 when the phase difference Df between the current flowing through the starting winding B2 and the internal timebase Tref presents null variation, this condition being set to represent a state of operation where the motor has completed its acceleration.

[0040] Thus, the electronic signal-processing device 30 via the control terminal 26 issues a command to the start switch S1 to open and remain in this state, terminating the supply of current to the starting winding B2, and therefore the motor start.

[0041] In the present invention there is further provided a step (j) to keep the start switch S1 open until the alternate voltage source signal F, or the power supplied is stopped over a stoppage period Tpara sufficient to characterize the stoppage of the motor.

[0042] Furthermore, the present method also comprises the step after motor start-up, to analyze time periods, or instances, in which the zero-crossing occurs at a voltage Vpar on the start switch S1. Thus, the start switch S1 is held closed during the start of the motor and open over the entire time that the motor is operating, so that the electronic signal-processing device 30 records voltage zero-crossing instances on said start switch S1 through a source terminal 25 and a voltage zero-crossing sensor SV capable of detecting the motor's operating state and recognizing its deceleration or shut-down through the interruption of power supplied by alternate voltage supply source F.

[0043] The method proposed herein also provides the steps for storing the internal timebase Tref, and synchronizing it with the voltage zero-crossing of starting winding B2. Figure 3 shows a graph where it is possible to display the setting of the timebase carried by the electronic signal-processing device 30, in accordance with the object of the present invention.

[0044] In relation to the aforementioned, it is noteworthy that with each new motor start-up a new timebase, or reference point, is created and stored by the electronic device 30 so that the circuit automatically adapts to new system load conditions, in particular supply voltage (overvoltage or undervoltage) and temperature conditions of the running winding B1 and the starting winding B2 of the stator.

[0045] Due to the record created for each new start cycle, the circuit does not require any prior calibration to operate with a given type of motor, as currently occurs in other prior art solutions, thus facilitating its use in a wide range of motors.

[0046] In the event of an unsuccessful attempt at start-up or ignition in which the rotor remains locked and there is no change in phase difference Df, the electronic signal-processing device 30 instructs the opening of start switch S1, when the time from the closing of start switch S1 exceeds a pre-determined maximum time value for completion of motor start-up. In this condition, the time interval E1 shown in Figure 2 will extend unduly, reaching a maximum allowable time and the opening of the start switch S1 will protect the start switch itself.

[0047] Therefore, based on the above, the present method provides a step capable of determining the opening of start-switch S1, through the starting device 28, when a time counted from the closing of start switch S1, exceeds a preset maximum time-value Tmax for completion of motor start-up.

[0048] In this case, the circuit will delay for a period appropriate for the cooling of the motor and/or required to adjust the load condition to the torque supplied by the motor, before allowing a new start cycle. In order to complete this last operation, the proposed method provides a step relating to the delay for the cooling of the motor Tres, and/or minimum load time Tmin, required establishing the load condition to the torque provided by the motor before allowing a new start cycle.

[0049] Finally, the instant invention provides a system for starting a single-phase induction motor, this motor being having a rotor and a stator M. The stator comprises a running winding B1 and a starting winding B2 as mentioned above.

[0050] In greater detail, and as illustrated in Figure 1, it is noted that this system comprises a start switch S1 linked electrically through its contact terminals to an alternate voltage source F. Said start switch S1 is configured to electrically connect a first terminal of the starting winding B2 to alternate voltage source F.

[0051] In the same Figure 1 one can observe in the system herein proposed the presence of a direct current source 29 supplied from the contact terminals of the start switch S1.

[0052] In this system there is also provision, as mentioned earlier, for at least one electronic signal processor 30, fed by direct current source 29, and operably linked to the start switch S1.

[0053] Additionally, a voltage zero-crossing sensor RS of the starting winding B2 is provided in the current starting system, configured to detect periods of time or instances in which the current in the starting winding B2 crosses zero. A voltage zero-crossing sensor SV connected to the terminals of the start switch S1 is also provided in this system, this sensor being configured to detect periods of time or moments in which the voltage between the terminals of the start switch S1 crosses zero.

[0054] In a very efficient and functional manner, the starting system, the object of the present invention, is configured to close the start switch S1 in order to start the supply of current to the starting winding B2 of the motor when starting the engine. In a very innovative manner with regards to the solutions available today, the aforementioned system is further configured to open the start switch S1 from a detected phase difference Df between the current circulating in the starting winding B2 and the internal time base Tref.

[0055] The opening of the starter S1 is established when the phase difference Df calculated above is greater than a predetermined phase limit Lfase.

[0056] From the configuration for the starting system of the present invention, it can be stated that the start switch S1, direct current source 29, electronic signal-processing device 30 and the voltage zero-crossing sensor RS and the voltage zero-crossing sensor SV form, in combination, a starting device 28.

[0057] Figure 1 also shows that a first terminal of AC voltage supply source F is electrically linked to a first gear terminal 45 of the running winding B1 and a first switch terminal S1' of the start switch S1. The first source terminal 1 is also associated to a first direct source terminal 27 of the direct current source 29.

[0058] Still in Figure 1, one can see that a second direct current source terminal 25 is electrically linked to a second terminal switch S1" of the start switch S1.

[0059] Regarding the control of said start switch S1, it is noted that this is operably linked to the electronic signal-processing device 30 via a control terminal 26 of the start switch S1.

[0060] In its operational form, the present system employs, as illustrated in Figures 2 and 3, the electronic signal-processing device 30 so as to create an internal time base Tref by the so-called starting device 28, with this timebase Tref being synchronized with a signal voltage phase of the alternate voltage source F.

[0061] In this regard, the electronic signal-processing device 30 determines the moments of opening and closing of the start switch S1 based on a calculated phase difference Df between the phase of current flowing through the starting winding B2 and the internal timebase Tref.

[0062] Furthermore, the electronic signal-processing device 30 is configured to keep the start switch S1 open until the power supplied by alternating current source F is interrupted for a period of time which features the motor stoppage.

[0063] Figure 1 further illustrates that the present system provides for the use of an operation capacitor CR positioned parallel to the terminals of the running winding B1 and starting winding B2 of the stator M in such a way as to provide a phase difference between the currents that pass through the running winding B1 and the starting winding B2.

[0064] Finally, the present invention achieves its objects in that it provides a starting mechanism, comprising a system, method and device for starting a single-phase motor, that is substantially more efficient and simplified compared to solutions known as the state of the art, as well as being capable of offering a more optimized start for a wide power range of motors of that type.

[0065] Having described an example of its preferred embodiment, it must be understood that the scope of the present invention includes other possible variations, being limited only by the content of the claims, which include therein possible equivalents.

Claims

1. A method for starting a single-phase induction motor, the motor comprising a rotor and a stator (M) with a running winding (B1) and a starting winding (B2), the running winding (B1) and the starting winding (B2) being connected in parallel to an alternate voltage power supply (F), the starting winding (B2) being electrically linked with a starting device (28), the starting device comprising a start switch (S1) allowing connecting and disconnecting the starting winding (B2) to/from the voltage power supply (F) under the control of an electronic signal-processing device (30), the starting device (28) comprising a source of direct current (29) supplied from the terminals of the start switch (S1) the electronic-signal processing device (30) being supplied by the source of direct current (29), the starting method being characterized by comprising the steps of:

a-) firstly measuring via the starting device (28), the voltage between the terminals of the start switch (S1) and computing and storing an internal timebase (Tref) by the electronic signal processing device (30) based on a plurality of detected time instants when this voltage crosses zero before closing the start switch (S1), the internal timebase (Tref) being synchronized with the phase of the voltage power source (F),

b-) closing the start switch (S1), for initiating the supply of current to the starting winding (B2) of the motor;

c-) measuring one or more starting time instants (Tpar) of the current in the starting winding (B2) where this crosses zero;

d-) comparing the time instants (Tpar) where the current flowing through the starting winding (B2) crosses zero with the internal timebase (Tref);

e-) calculating, via the starting device (28), a phase difference Df between the current flowing through the starting winding (B2) and the internal timebase (Tref) based on the comparison made in Step d

f-) opening the start switch (S1) based on the calculation in Step e when the starting device (28) detects the phase difference (Df) between the current flowing through the starting winding (B2) and the internal timebase (Tref) of a value in excess of a predetermined start phase boundary.

2. The method, in accordance with Claim 1, characterized by the predetermined starting phase boundary that depicts an operating state in which the motor is accelerated at a rotational speed close to its nominal operating speed.

3. The method, in accordance with Claims 1 and 2, characterized by the opening of the start switch (S1) that occurs from a command sent via the electronic signal-processing device (30), which is contained within the starting device (28), at the moment when the motor is accelerated at a rotational speed close to the nominal speed.

4. The method, in accordance with Claim 1, characterized by further comprising a step of:

g) opening the start switch (S1) when the phase difference (Df) between the current flowing through the starting winding (B2) and the internal timebase (Tref) is greater than a predetermined phase value, which is configured to represent a state in which the motor is accelerated to a rotational speed close to its nominal speed after the expiry of a predefined starting time.

5. The method, in accordance with Claim 1, characterized by including a further step of:

h) opening the start switch (S1) when the phase difference (Df) between the current flowing through the starting winding (B2) and the internal time base (Tref) shows no change, this condition being configured to represent an operation in which the motor has completed its acceleration.

6. The method, according to any one of Claim 1, characterized by further comprises the step of:

i) keeping the start switch open until the signal voltage of the alternate voltage source (F) is interrupted for a period of time of stoppage sufficient to features a stoppage of the motor.

7. The method, in accordance with any one of the above claims characterized by comprising the further step of, analyzing, after motor startup, the time instants, or moments, in which voltage zero-crossing occurs above the start switch (S1).

8. The method, in accordance with any one of claims 1 through 7, characterized by further comprising the step of:

- storing the internal timebase (Tref); and

- synchronizing the time internal reference (Tref) with the voltage zero-crossing of the starting winding (B2).

9. The method, in accordance with any of the Claims 1 through 8, characterized by further comprising the step of:

- determining the opening of the start switch (S1) via the starting device (28) where a duration counted from the closing of the start switch (S1) exceeds a maximum time value (Tmax) previously defined for the completion of motor start-up.

10. The method, in accordance with Claim 9, characterized by further comprising a step of waiting some time for the cooling of the motor (Tres), and/or a minimum load time (Tmin) configured to establish the load condition to the torque supplied by the motor, before beginning a new starting cycle.

11. A system for starting a single-phase induction motor, the motor comprising a rotor and a stator (M) with a running winding (B1) and a starting winding (B2), the running winding (B1) and the starting winding (B2) being connected in parallel to an alternate voltage power supply (F), the system being characterized by comprising:

- a start switch (S1) associated electrically via its contact terminals to the source of alternate voltage (F), the start switch (S1) allowing connecting and disconnecting the starting winding to/from the alternate voltage power supply (F) under the control of an electronic signal-processing device (30);

- a source of direct current (29) supplied by the contact terminals of the start switch (S1);

- the electronic signal-processing device (30), supplied by the direct current source (29) and operably linked to the start switch (S1);

- a current zero-crossing sensor (RS) configured to detect periods of time or time instants in which the current of the starting winding (B2) crosses zero; and

- a voltage zero-crossing sensor (VS) at the terminals of the start switch (S1) configured to detect periods of time or time instants in which the voltage between the terminals of the start switch (S1) crosses zero;

- the system being configured that the voltage between the terminals of the start switch (S1) is measured and an internal timebase (Tref) is computed and stored by the electronic signal processing device (30) based on a plurality of detected time instants when this voltage crosses zero before closing the start switch (S1), the internal timebase (Tref) being synchronized with the phase of the alternate voltage power supply (F);

- the system being configured to close the start switch (S1) in order to initiate supply of current to the starting winding (B2) of the motor;

- the system being configured to open the start switch (S1) at the detection of a phase difference (Df) between the current flowing in the starting winding (B2) and the internal timebase (Tref) of a value in excess of a predetermined start phase boundary.

12. The starting system, in accordance with Claim 11, characterized by the opening of the start switch (S1) that is established when the phase difference (Df) calculated is over a predetermined phase limit (Lfase).

13. The starting system, in accordance with Claim 11, characterized by the start switch (S1), the source of direct current supply (29), the electronic signal-processing device (30) of the current zero-crossing sensor (RS) and a voltage zero-crossing sensor (SV) form, in combination, a starting device (28).

14. The starting system, in accordance with Claim 11, characterized by a first supply terminal (1) of the alternate voltage supply source (F) that is linked electrically to a first gear terminal (45) of the running winding (B1) and a first switch terminal (S1') of the start switch (S1).

15. The starting system, in accordance with Claim 14, characterized by the first source terminal (1) that is linked to a first direct current terminal (27) of the direct current source (29).

16. The starting system, in accordance with Claim 11, characterized by electronic signal-processing device (30) that is operably linked to the start switch (S1) through a control terminal (26) of the start switch (S1).

17. The starting system, in accordance with Claim 13, characterized by the electronic signal-processing device (30) that creates an internal time base (Tref) through a starting device (28), and this reference time synchronized with an alternate voltage signal phase of the AC power source (F).

18. The starting system, in accordance with Claim 11, characterized by the electronic signal-processing device (30) that determines the moment of opening and closing of the start switch (S1) based on a phase difference (Df) calculated between the phase of current flowing through the starting winding (B2) and the voltage phase in the alternate voltage source (F).

19. The starting system, in accordance with Claim 11, characterized by the electronic signal-processing device (30) that is configured to maintain the start switch (S1) in the open state until the power supplied by the alternate voltage source (F) is interrupted for a period of time which features motor stoppage.

20. The starting system, in accordance with Claim 11, characterized by further comprising an operating capacitor (CR) arranged parallel to the terminals of the running winding (B1) and the starting winding (B2) of the stator (M), so as to provide a phase difference between the currents passing through the running (B1) and starting (B2) windings.

Ansprüche

1. Verfahren zum Starten eines Einphasen-Induktionsmotors, wobei der Motor einen Rotor und einen Stator (M), eine Laufwicklung (B1) und eine Startwicklung (B2) aufweist, die Laufwicklung (B1) und die Startwicklung (B2) parallel mit einer Wechselstromquelle (F) verbunden sind, die Startwicklung (B2) elektrisch verbunden mit einer Startvorrichtung (28) ist, die Startvorrichtung einen Startschalter (S1) umfasst, der das Verbinden oder Trennen der Startwicklung (B1) mit oder von der Stromquelle (F) kontrolliert durch ein elektronisches Signalverarbeitungsgerät (30) erlaubt, die Startvorrichtung (28) Gleichstrom (29) von den Anschlüssen des Startschalters (S1) bezieht, das elektronische Signalverarbeitungsgerät (30) mit Gleichstrom versorgt wird, und das Startverfahren dadurch gekennzeichnet ist, dass es die folgenden Schritte enthält:

(a) zunächst die Bestimmung der Spannung zwischen den Anschlüssen des Startschalters (S1) mit Hilfe der Startvorrichtung (28) und Berechnen und Speichern eines internen Prüfzeitraums (Tref) mit Hilfe des elektronischen Signalverarbeitungsgerätes (30) basierend auf einer Vielzahl von aufgezeichneten Zeitpunkten, an denen die Spannung den Wert Null durchläuft bevor der Startschalter (S1) schließt, wobei der interne Prüfzeitraum (Tref) mit der Phase der Stromquelle (F) synchronisiert wird;

(b) Schließen des Startschalters (S1), um die Bereitstellung von Strom für die Startwicklung (B2) des Motors in Gang zu setzen;

(c) Bestimmung von einem oder mehreren Startzeitpunkten (Tpar) des Stroms in der Startwicklung (B2), wenn dieser den Wert Null durchläuft;

(d) Vergleichen der Zeitpunkte (Tpar), an denen der Strom, der durch die Startwindung (B2) fließt, den Wert Null durchläuft mit dem internen Prüfzeitraum (Tref);

(e) Berechnen einer Phasendifferenz (Df) zwischen dem Strom, der durch die Startwicklung (B2) fließt und dem internen Prüfzeitraum (Tref) mit Hilfe der Startvorrichtung (28) basierend auf dem Vergleich, der in Schritt (d) durchgeführt worden ist;

(f) Öffnen des Startschalters (S1) basierend auf der Berechnung in Schritt (e) sobald die Startvorrichtung (28) eine Phasendifferenz (Df) zwischen dem Strom, der durch die Startwicklung (B2) fließt und dem internen Prüfzeitraum (Tref) feststellt, die einen zuvor festgelegten Startphasengrenzwert überschreitet.

2. Das Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der zuvor festgelegte Startphasengrenzwert den Betriebszustand beschreibt, in dem der Motor auf eine Rotationsgeschwindigkeit beschleunigt, die nahe an der üblichen Betriebsgeschwindkeit liegt.

3. Das Verfahren nach den Ansprüchen 1 und 2, dadurch gekennzeichnet, dass das Öffnen des Startschalters (S1) durch die Aussendung eines Befehls durch das elektronische Signalverarbeitungsgerät (30), welches in der Startvorrichtung (28) enthalten ist, in dem Moment erfolgt, in dem der Motor auf eine Rotationsgeschwindigkeit beschleunigt, die nahe an der üblichen Betriebsgeschwindkeit liegt.

4. Das Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass es weiterhin den folgenden Schritt aufweist:

(g) Öffnen des Startschalters (S1), sobald die Phasendifferent (Df) zwischen dem Strom, der durch die Startwicklung (B2) fließt und der interne Prüfzeitraum (Tref) größer als ein vorbestimmter Phasenwert ist, welcher ausgelegt ist, um einen Zustand abzubilden, in welchem der der Motor nach einer vorbestimmten Startzeit auf eine Rotationsgeschwindigkeit beschleunigt, die nahe an der üblichen Betriebsgeschwindkeit liegt.

5. Das Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass es weiterhin den folgenden Schritt aufweist:

(h) Öffnen des Startschalters (S1), wenn die Phasendifferent (Df) zwischen dem Strom, der durch die Startwicklung (B2) fließt und der interne Prüfzeitraum (Tref) keine Änderung aufweist, wobei diese Bedingung den Zustand abbildet, in dem der Motor seine Beschleunigung abgeschlossen hat.

6. Das Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass es weiterhin den Schritt aufweist:

(i) Offenhalten des Startschalters bis die Signalspannung der Wechselstromquelle (F) für einen Stopzeitraum unterbrochen wird, der ausreichend ist, um ein Anhalten des Motors zu bewirken.

7. Das Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass es als weiteren Schritt nach Ingangsetzung des Motors die Analyse der Zeitpunkte oder Momente umfasst, in denen die Spannung am Startschalter (S1) den Wert Null durchläuft.

8. Das Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass es weiterhin den Schritt aufweist:

Speichern des internen Prüfzeitraums (Tref); und

Synchronisation des internen Prüfzeitraums (Tref) mit dem Durchgang der Spannung an der Startwicklung (B2) durch den Nullpunkt;

9. Das Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass es weiterhin den Schritt aufweist:

Bestimmung der Öffnung des Startschalters (S1) mit Hilfe der Startvorrichtung (28), sobald die Zeitdauer beginnend ab dem Schließen des Startschalters (S1) einen maximalen Zeitraum (Tmax) überschreitet, der zuvor für die Beendung des Motorstarts festgelegt worden war.

10. Das Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass es weiterhin einen Schritt aufweist, gemäß dem eine Zeit für das Abkühlen des Motors (Tres) gewartet wird und/oder eine Mindestbelastungszeit (Tmin) vorgegeben wird, die ausgelegt ist, um die Belastungsbedingungen im Zusammenhang mit dem vom Motor bewirkten Drehmoment abzubilden, bevor ein neuer Startzyklus begonnen wird.

11. Startvorrichtung für einen Einphasen-Induktionsmotor, wobei der Motor einen Rotor und einen Stator (M), eine Laufwicklung (B1) und eine Startwicklung (B2) aufweist, die Laufwicklung (B1) und die Startwicklung (B2) parallel mit einer Wechselstromquelle (F) verbunden sind, dadurch gekennzeichnet, dass die Vorrichtung umfasst:

- einen Startschalter (S1) in elektrischer Verbindung über seine Anschlüsse mit einer Wechselstromquelle (F), wobei der Startschalter (S1) das Verbinden oder Trennen der Startwicklung (B1) mit oder von der Stromquelle (F) kontrolliert durch ein elektronisches Signalverarbeitungsgerät (30) erlaubt,

- eine Gleichstromquelle (29), die durch die Anschlüsse des Startschalters (S1) zur Verfügung gestellt wird;

- das elektronische Signalverarbeitungsgerät (30), das durch die Gleichstromquelle (29) versorgt und operabel mit dem Startschalter (S1) verbunden ist;

- einen Sensor zur Bestimmung des Strom-Nulldurchgangs (RS), der zur Bestimmung der Zeiträume ausgelegt ist, in denen der Strom der Startwicklung (B2) den Wert Null durchläuft; und

- einen Sensor zur Bestimmung des Spannungs-Nulldurchgangs (VS) an den Anschlüssen des Startschalters (S1), der zur Bestimmung der Zeiträume ausgelegt ist, in denen die Spannung zwischen den Anschlussstellen des Startschalters (S1) den Wert Null durchläuft;

- wobei die Vorrichtung so beschaffen ist, dass die Spannung zwischen den Anschlüssen des Startschalters (S1) gemessen wird und ein interner Prüfzeitraum (Tref) durch das elektronische Signalverarbeitungsgerät (30) berechnet und gespeichert wird, basierend auf einer Vielzahl von Zeitpunkten, an denen die Spannung vor dem Schließen des Startschalters (S1) den Wert Null durchläuft, und der interne Prüfzeitraum mit der Phase der Wechselstromquelle (F) synchronisiert wird;

- wobei die Vorrichtung so beschaffen ist, dass der Startschalter (S1) geschlossen werden kann, um die Stromversorgung für die Startwicklung (B2) des Motors In Gang zu setzen;

- wobei die Vorrichtung so beschaffen ist, dass der Startschalter (S1) geöffnet wird, wenn eine Phasendifferenz (Df) zwischen dem Strom, der durch die Startwicklung (B2) fließt und dem internen Prüfzeitraum (Tref) festgestellt wird, die einen zuvor festgelegten Startphasengrenzwert überschreitet.

12. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass der Startschalter (S1) geöffnet wird, wenn die berechnete Phasendifferenz (Df) eine vorgegebene Phasengrenze (Lfase) überschreitet.

13. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass der Startschalter (S1), die Gleichstromquelle (29), das elektronische Signalverarbeitungsgerät (30), der Strom-Nullpunktdurchgangssensor (RS) und der Spannungs-Nullpunktdurchgangssensor (SV) gemeinsam eine Startvorrichtung (28) bilden.

14. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass sie einen ersten Versorgungsanschluss (1) für die Wechselstromquelle (F) aufweist, welcher elektrisch verbunden mit einem ersten Antriebsanschluss (45) der Laufwicklung (B1) ist, sowie einen ersten Schalteranschluss (S1') für den Startschalter (S1) enthält.

15. Die Startvorrichtung nach Anspruch 14, dadurch gekennzeichnet, dass der erste Versorgungsanschluss (1) mit einem ersten Gleichstromanschluss (27) der Gleichstromquelle (29) verbunden ist.

16. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass das elektronische Signalverarbeitungsgerät (30) operabel über einen Kontrollanschluss (26) des Startschalters (S1) verbunden ist.

17. Die Startvorrichtung nach Anspruch 13, dadurch gekennzeichnet, dass das elektronische Signalverarbeitungsgerät (30) mit Hilfe einer Startvorrichtung (28) einen internen Prüfzeitraum (Tref) bestimmt und diese Vergleichszeit synchronisiert wird mit der Wechselstromsignalphase der Wechselstromquelle (F).

18. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass das elektronische Signalverarbeitungsgerät (30) den Moment des Öffnen und Schließen des Startschalters (S1) auf der Grundlage einer Phasendifferenz (Df) zwischen der Phase des Stroms, der durch die Startwicklung (B2) und der Spannungsphase der Wechselstromquelle (F) berechnet.

19. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass das elektronische Signalverarbeitungsgerät (30) ausgelegt ist, den Startschalter (S1) in der geöffneten Stellung zu halten, bis die Stromversorgung durch die Wechselstromquelle (F) für einen Zeitraum unterbrochen wird, der ausreichend ist, um den Motor anzuhalten.

20. Die Startvorrichtung nach Anspruch 11, dadurch gekennzeichnet, dass sie weiterhin einen in Betrieb befindlichen Kondensator (CR) aufweist, der parallel zu den Anschlüssen der Laufwicklung (B1) und der Startwicklung (B2) des Motors angeordnet ist, um eine Phasendifferenz zwischen den Strömen zwischen der Lauf- (B1) und der Startwicklung (B2) zu bewirken.

Revendications

1. Procédé pour démarrer un moteur à introduction monophasé, le moteur comprenant un rotor et un stator (M) avec un enroulement de fonctionnement (B1) et un enroulement de démarrage (B2), l'enroulement de fonctionnement (B1) et l'enroulement de démarrage (B2) étant connectés en parallèle à une alimentation en tension alternative (F), l'enroulement de démarrage (B2) étant connecté électriquement à un dispositif de démarrage (28), le dispositif de démarrage comprenant un commutateur de démarrage (S1) permettant de connecter et de déconnecter l'enroulement de démarrage (B2) à/de l'alimentation en tension (F) sous la commande d'un dispositif de traitement de signal électronique (30), le dispositif de démarrage (28) comprenant une source de courant continu (29) délivré à partir des bornes du commutateur de démarrage (S1), le dispositif de traitement de signal électronique (30) étant alimenté par la source de courant continu (29), le procédé de démarrage étant caractérisé en ce qu'il comprend les étapes :

a) d'abord, de mesure, par l'intermédiaire du dispositif de démarrage (28), de la tension entre les bornes du commutateur de démarrage (S1) et de calcul et de mémorisation d'une base de temps interne (Tref) par le dispositif de traitement de signal électronique (30) sur la base d'une pluralité d'instants détectés lorsque cette tension passe par zéro avant de fermer le commutateur de démarrage (S1), la base de temps interne (Tref) étant synchronisée avec la phase de la source d'alimentation en tension (F),

b) de fermeture du commutateur de démarrage (S1), pour lancer l'alimentation en courant de l'enroulement de démarrage (B2) du moteur ;

c) de mesure d'un ou de plusieurs instants de démarrage (Tpar) du courant dans l'enroulement de démarrage (B2) auxquels celui-ci passe par zéro,

d) de comparaison des instants (Tpar) auxquels le courant circulant à travers l'enroulement de démarrage (B2) passe par zéro avec la base de temps interne (Tref) ;

e) de calcul, par l'intermédiaire du dispositif de démarrage (28), d'une différence de phase Df entre le courant circulant à travers l'enroulement de démarrage (B2) et la base de temps interne (Tref) sur la base de la comparaison effectuée à l'étape d ;

f) d'ouverture du commutateur de démarrage (S1) sur la base du calcul effectué à l'étape e lorsque le dispositif de démarrage (28) détecte la différence de phase (Df) entre le courant circulant à travers l'enroulement de démarrage (B2) et la base de temps interne (Tref) d'une valeur dépassant une limite de phase de démarrage prédéterminée.

2. Procédé selon la revendication 1, caractérisé en ce que la limite de phase de démarrage prédéterminée représente un état de fonctionnement dans lequel le moteur est accéléré à une vitesse de rotation proche de sa vitesse de fonctionnement nominale.

3. Procédé selon les revendications 1 et 2, caractérisé en ce que l'ouverture du commutateur de démarrage (S1) est produite par une commande envoyée par l'intermédiaire du dispositif de traitement de signal électronique (30), qui est contenu dans le dispositif de démarrage (28), au moment auquel le moteur est accéléré à une vitesse de rotation proche de la vitesse nominale.

4. Procédé selon la revendication 1, caractérisé en ce qu'il comprend en outre une étape :

g) d'ouverture du commutateur de démarrage (S1) lorsque la différence de phase (Df) entre le courant circulant à travers l'enroulement de démarrage (B2) et la base de temps interne (Tref) est supérieure à une valeur de phase prédéterminée, qui est configurée pour représenter un état dans lequel le moteur est accéléré à une vitesse de rotation proche de sa vitesse nominale à la fin d'un temps de démarrage prédéfini.

5. Procédé selon la revendication 1, caractérisé en ce qu'il comprend une étape supplémentaire :

h) d'ouverture du commutateur de démarrage (S1) lorsque la différence de phase (Df) entre le courant circulant à travers l'enroulement de démarrage (B2) et la base de temps interne (Tref) ne présente aucun changement, cette condition étant configurée pour représenter un fonctionnement dans lequel le moteur a achevé son accélération.

6. Procédé selon la revendication 1, caractérisé en ce qu'il comprend en outre l'étape :

i) de maintien du commutateur de démarrage ouvert jusqu'à ce que la tension de signal de la source de tension alternative (F) soit interrompue pendant une période de temps d'arrêt suffisante pour caractériser un arrêt du moteur.

7. Procédé selon l'une quelconque des revendications ci-dessus, caractérisé en ce qu'il comprend l'étape supplémentaire d'analyse, après le démarrage du moteur, des instants, ou des moments auxquels un passage par zéro de la tension se produit sur le commutateur de démarrage (S1).

8. Procédé selon l'une quelconque des revendications 1 à 7, caractérisé en ce qu'il comprend en outre l'étape :

- de mémorisation de la base de temps interne (Tref) ; et

- de synchronisation de la référence de temps interne (Tref) avec le passage par zéro de la tension de l'enroulement de démarrage (B2).

9. Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il comprend en outre l'étape :

- de détermination de l'ouverture du commutateur de démarrage (S1) par l'intermédiaire du dispositif de démarrage (28) lorsqu'une durée comptée à partir de la fermeture du commutateur de démarrage (S1) dépasse une valeur de temps maximum (Tmax) définie au préalable pour l'achèvement du démarrage du moteur.

10. Procédé selon la revendication 9, caractérisé en ce qu'il comprend en outre une étape d'attente d'un certain temps pour le refroidissement du moteur (Tres), et/ou d'un temps en charge minimum (Tmin) configuré pour établir la condition de charge au couple fourni par le moteur, avant de débuter un nouveau cycle de démarrage.

11. Système pour démarrer un moteur à introduction monophasé, le moteur comprenant un rotor et un stator (M) avec un enroulement de fonctionnement (B1) et un enroulement de démarrage (B2), l'enroulement de fonctionnement (B1) et l'enroulement de démarrage (B2) étant connectés en parallèle à une alimentation en tension alternative (F), le système étant caractérisé en ce qu'il comprend :

- un commutateur de démarrage (S1) associé électriquement, par l'intermédiaire de ses bornes de contact, à la source de tension alternative (F), le commutateur de démarrage (S1) permettant de connecter et de déconnecter l'enroulement de démarrage à/de l'alimentation en tension alternative (F) sous la commande d'un dispositif de traitement de signal électronique (30) ;

- une source de courant continu (29) délivré par les bornes de contact du commutateur de démarrage (S1) ;

- le dispositif de traitement de signal électronique (30), alimenté par la source de courant continu (29) et connecté fonctionnellement au commutateur de démarrage (S1) ;

- un capteur de passage par zéro du courant (RS) configuré pour détecter des périodes de temps ou des instants auxquels le courant de l'enroulement de démarrage (B2) passe par zéro ; et

- un capteur de passage par zéro de la tension (VS) aux bornes du commutateur de démarrage (S1) configuré pour détecter les périodes de temps ou les instants auxquels la tension entre les bornes du commutateur de démarrage (S1) passe par zéro ;

- le système étant configuré en ce que la tension entre les bornes du commutateur de démarrage (S1) est mesurée et une base de temps interne (Tref) est calculée et mémorisée par le dispositif de traitement de signal électronique (30) sur la base d'une pluralité d'instants détectés auxquels cette tension passe par zéro avant la fermeture du commutateur de démarrage (S1), la base de temps interne (Tref) étant synchronisée avec la phase de l'alimentation en tension alternative (F) ;

- le système étant configuré pour fermer le commutateur de démarrage (S1) afin de lancer l'alimentation en courant de l'enroulement de démarrage (B2) du moteur ;

- le système étant configuré pour ouvrir le commutateur de démarrage (S1) lors de la détection d'une différence de phase (Df) entre le courant circulant dans l'enroulement de démarrage (B2) et la base de temps interne (Tref) d'une valeur dépassant une limite de phase de démarrage prédéterminée.

12. Système de démarrage selon la revendication 11, caractérisé en ce que l'ouverture du commutateur de démarrage (S1) est établie lorsque la différence de phase (Df) calculée dépasse une limite de phase prédéterminée (Lfase).

13. Système de démarrage selon la revendication 11, caractérisé en ce que le commutateur de démarrage (S1), la source d'alimentation en courant continu (29), le dispositif de traitement de signal électronique (30) du capteur de passage par zéro du courant (RS) et un capteur de passage par zéro de la tension (SV) forment, en combinaison, un dispositif de démarrage (28).

14. Système de démarrage selon la revendication 11, caractérisé en ce qu'une première borne d'alimentation (1) de la source d'alimentation en tension alternative (F) est connectée électriquement à une première borne d'enroulement (45) de l'enroulement de fonctionnement (B1) et à une première borne de commutateur (S1') du commutateur de démarrage (S1).

15. Système de démarrage selon la revendication 14, caractérisé en ce que la première borne de source (1) est connectée à une première borne de courant continu (27) de la source de courant continu (29).

16. Système de démarrage selon la revendication 11, caractérisé en ce que le dispositif de traitement de signal électronique (30) est connecté fonctionnellement au commutateur de démarrage (S1) par l'intermédiaire d'une borne de commande (26) du commutateur de démarrage (S1).

17. Système de démarrage selon la revendication 13, caractérisé en ce que le dispositif de traitement de signal électronique (30) crée une base de temps interne (Tref) par l'intermédiaire d'un dispositif de démarrage (28), et ce temps de référence est synchronisé avec une phase du signal de tension alternative de la source d'alimentation alternative (F).

18. Système de démarrage selon la revendication 11, caractérisé en ce que le dispositif de traitement de signal électronique (30) détermine le moment d'ouverture et de fermeture du commutateur de démarrage (S1) sur la base d'une différence de phase (Df) calculée entre la phase du courant circulant à travers l'enroulement de démarrage (B2) et la phase de la tension dans la source de tension alternative (F).

19. Système de démarrage selon la revendication 11, caractérisé en ce que le dispositif de traitement de signal électronique (30) est configuré pour maintenir le commutateur de démarrage (S1) dans l'état ouvert jusqu'à ce que la puissance fournie par la source de tension alternative (F) soit interrompue pendant une période de temps qui caractérise un arrêt du moteur.

20. Système de démarrage selon la revendication 11, caractérisé en ce qu'il comprend en outre un condensateur de fonctionnement (CR) agencé en parallèle avec les bornes de l'enroulement de fonctionnement (B1) et de l'enroulement de démarrage (B2) du stator (M), de manière à fournir une différence de phase entre les courants passant à travers les enroulements de fonctionnement (B1) et de démarrage (B2).

Drawing